\begin{itemize}
  \item Relax the evolution conditions for the property, in the extreme there
  will only be a mapping between the properties for entity $e_n$ and entity
  $e_{n+1}$ and the hypothesis is that $(p,p')$ belonging to the mapping means
  that $p$ has the same semantics in $e_n$ as $p'$ has in $e_{n+1}$.
  \item Relax the monotonicity of the satisfaction of properties between entity
  $e_n$ and entity $e_{n+1}$. This means that a property can be satisfied in
  entity $e_n$ but will stop being satisfied in entity $n+1$. This corresponds
  to requirements being dropped or replaced by others as the system evolves.
\end{itemize}